The present invention relates to a liquid-cooled internal combustion engine comprising an engine block, which includes a plurality of cylinders, and cylinder heads closing the cylinders, wherein each cylinder is surrounded by a respective cooling liner and each cylinder head has provided therein at least one separate cooling chamber connected to the cooling liner of the associated cylinder via at least one transition channel.
For cooling an internal combustion engine during engine operation, a suitable coolant flows through the engine. Due to a cooling liner surrounding the cylinder sleeves installed in the cast part of the engine block, coolant flows around the cylinder sleeves. Also the cylinder heads comprise one or more cooling chambers for cooling the valves, gaskets, etc. accommodated therein. Normally, an external coolant pump is used for pumping the coolant through the cooling liners, cooling chambers and channels of the individual cylinders.
A possible cooling concept for an internal combustion engine is known from EP 2 132 423 B1. The flow pattern according to the prior art is schematically shown in FIG. 1. Each of the total number of four cylinders of the engine block 1 is closed via a single cylinder head 3. The cooling liners of the cylinders are identified by reference numeral 2. Starting from a common coolant distribution chamber 5, the coolant is first subdivided into partial flows through the individual cooling liners 2 of the cylinders of the engine block 1. The coolant flows from each cooling liner 2 through a separate riser 6 into first and second cooling subchambers 7a, 7b of the respective cylinder head 3. At the end, the coolant of the partial flows is collected in a common coolant collecting chamber 8.
Ideally, the partial flows of coolant distributed to the individual cylinders should be identical and pressure losses should be kept low. However, manufacturing tolerances in the casting process for producing the engine block 1 and the cylinder heads 3 and the cylinder head bank 200 lead to minor deviations of the actually existing geometries of the cooling liners, cooling chambers and cooling channels, which deviations are already application relevant and may cause asymmetric partial flows with deviating coolant flow rates. Furthermore, when the supply of coolant into the distributing chamber and the discharge of the coolant from the collecting chamber are inclusively taken into account, the flow paths to be assigned to the individual cylinders are not identical. The asymmetries require, all in all, a higher coolant circulation rate, so as to guarantee sufficient cooling of all combustion chamber surroundings.
Up to now, this has been remedied by modifying the cylinder head gaskets, which are identified by reference numeral 4 in FIG. 1. These cylinder head gaskets comprise, inter alia, openings for the coolant transition channels 6, 9 between the engine block 1 and the cylinder head 3. By adapting the gasket elements 4a, 4b in the areas of the channels 6, 9, individual flow resistances can be realized, whereby a flow rate adaptation of the various partial flows of coolant can be accomplished in the final analysis. This measure will also be necessary when the upper or lower cooling chambers 7a, 7b are in direct fluid communication with one another.
The suggested course of action is, however, disadvantageous insofar as it requires first a complicated analysis of the symmetry characteristics of the internal combustion engine produced. In addition, the necessity of providing cylinder-specific gaskets is not particularly economical.